The Funambol SyncML server might be a great product, but it just
doesn’t work for me. I had promised to have a closer look at it, and
initial dry runs against Funambol with Lotus Domino looked quite
promising. After getting my Nokia N70 I attempted to get it to
synchronize with Funambol, but that didn’t work out as smoothly as I’d
expected. The plugins for BlackBerry don’t work at all; the sync4j version
at least attempts a connection, whereas the Funambol version doesn’t. Oh,
and while I’m ranting, I couldn’t get Nexthaus’ SyncJe Client for Lotus
Notes to do anything against any SyncML server I tried. What did work (a
bit) was Tsync, the SyncML extension for Mozilla Thunderbird;
interesting though, what the author has to say about Funambol! It was a bad
weekend as far as SyncML goes… ;-) 
One bright light did shine
though: the Swiss Synthesis AG have a product named Synthesis SyncML
Server, which worked immediately. I had a look at both the Windows and
the Linux versions (2.1.1.28), and the product works as advertised. The
product isn’t quite inexpensive; it starts out at around EUR 1950, but their
demo is available at no cost to use (the program does announce Demo Version
Expiring after 2006-12-31). The demo version doesn’t use an ODBC datastore,
relying on tab-separated CSV files instead, which is probably more than enough
for a single user. Unfortunately, while attempting to synchronize a second
mobile phone, I screwed the missus’ address book; although using a
userauth.txt file for user authentication, I couldn’t get Synthesis to
separate our databases from eachother; I hope that is simply a
misconfiguration on my part; does anybody know whether the demo version
supports multi-user? What I also liked was the single binary and the single
XML configuration file which is very clearly commented. Synthesis also has a
version which can run under control of the Apache web server, but
unfortunately I couldn’t test that as it belongs to the “PRO” version. That is
the version I’d really like to have for about five to ten users, and of course
at no expense. :-) I note, that the SyncML Compliant Products page lists
Synthesis AG but neither Funambol nor its older name sync4j.
Update: c’t 14/2006 has an article describing the installation of
the Synthesis SyncML server and a pointer to a free license code for use of
the “PRO” version.